Femoropopliteal bypass grafts--an isotope technique allowing in vivo comparison of thrombogenicity.

Prosthetic femoropopliteal grafts attract platelet thrombus and often occlude in the months following implantation. Hence a technique to measure the in vivo thrombogenicity of different vascular substitutes in patients has been developed. In 28 patients the rate of accumulation of 111-indium-labelled platelets in saphenous vein, polytetrafluoroethylene (PTFE) and double velour Dacron femoropopliteal grafts was studied. One week postoperatively autologous 111In-labelled platelets were injected and the isotope emissions over the graft and contralateral leg counted. Graft thrombogenicity was calculated as the daily rise over 7 days in the ratio of counts over the graft to those over the contralateral leg. Mean thrombogenicity index (+/- s.e.mean) was greatest in the Dacron grafts at 0.24 +/- 0.03 which compared with 0.13 +/- 0.02 in PTFE (P less than 0.05). Saphenous vein was markedly less thrombogenic than either prosthetic graft with a mean index of only 0.025 +/- 0.01 (P less than 0.01). Platelet survival failed to differentiate the three graft materials, demonstrating that the direct measurement of 111In platelet deposition was a more sensitive technique.